How do I refute the assertion that Christ’s death on the cross removed everyone from that point after from original sin?
I think first and foremost its self evident in our inclination to sin which we must admit to the paradox following, we are sinners. That’s an important three words, we are sinners. And, most critical, we must not sin, forgiveness being a universal of Jesus Christ as is the New Testament.
Supernaturally infused Grace has a responsibility along with it to maintain it.
Even after Baptism we still have inclination to sin.
Exactly, even after the supernatural virtue imposed which in Baptism is freely given. Still sinners and now admittedly responsible by Christian identity. It makes the dynamic more alarming?
First thing is to explain Original Sin.
What is your explanation of Original Sin?
If the assertion is that Christ’s death put everyone in a state of grace (put everyone in a state so that, if they died in that state, they would go to heaven), I would reference the biblical passages stating the necessity of baptism and similar. If the assertion relates to the tendency to sin, I would say “look at the world.”